Electric immersion heater



p 9, 1939. w. H. BULPITT 2,173,708

ELECTR I G IMMERS ION HEATER Filed Sept. 12, 1938 UJaHeY Henni Immf. W vQfW Patented Sept. 19, 1939 UNITED STATES PATENT OFFICE ELECTRIC IMJVIERSION HEATER, Walter Henry Bulpitt, Birmingham, England Application September 12, 1938, Serial No. 229,624 In Great Britain October 28, 1937 8 Claims.

This invention relates to electric immersion heaters of the kind comprising a tubular metal j body of loop form, this looped body enclosing a in the vessel will uncover the heater, and hence allow the same to reach an excessive temperature, whilst there is still a considerable quantity of liquid remaining. Thus, as hitherto constructed, vessels fitted with immersion heaters of the type in question have the drawback that they cannot be operated unless the quantity of liquid therein is sufficient to cover the heater.

The object of the present invention is to provide a simple and effective means of obviating the above drawback.

Referring to the drawing:

Figure 1 is a part-sectional side elevation of a vessel provided with an immersion heater in accordance with the present invention.

Figure 2 is a part-sectional plan view of the same.

Figure 3 is a perspective view of the heater.

In the construction illustrated, the immersion heater includes a body 5 of loop form, such body being of metallic tubular construction and containing a resistance wire which may be wound upon a mica strip or other suitable support. The tube forming the body is seamless and has a flat section whose major dimension is substantially perpendicular to the plane of the loop. It will be seen that the loop is of part-circular shape, the terminal portions 6 of the body 5 being turned outwardly into substantially parallel relationship and secured to the inner end of a hollow metal plug 1.

This plug 1 is adapted for insertion in an opening 8 in the wall of a kettle or other vessel 9, and ,is provided with a shoulder III which abuts the inner face of such wall. The body of the plug 1 may be screw threaded to receive a nut I I which engages the outside of the vessel 9.

The ends of the resistance winding are connected to terminal pins I2 carried by an insulating block I3 in the outer end of the plug 1. The

fusible metal which melts temperature, so that the device then operates to 25 plug 1 conveniently forms one part of a coupling, the movable part of which carries sockets for engagement with the pins l 2 in known manner.

The tubular body 5 is provided with one or more downwardly projecting fins [4 contact with the liquid in the vessel 9 after the level of said liquid has descended below the body 5. In the convenient arrangement shown, two ,fins M of segmental shape are soldered to the underside of the body 5 at diametrically opposite 10 positions thereon, the curved edges of these fins being disposed close to the base of the vessel 9.

With immersion heaters of the kind to which the present invention relates, it is a common practice to provide a safety device whereby the current 1 is automatically out 01f when a certain temperature is reached, so that neither the heater nor the vessel itself can be damaged in the event of the heater being forgotten or neglected until all the liquid in the vessel has been evaporated.

Such a safety device may be employed in conjunction with a heater embodying the present invention, and may be of the kind containing a at a predetermined break the circuit through the heater.

I A suitable form of safety device is described in Letters Patent No. 1,887,082, issued to me on the 8th November, 1932, and it is preferred to arrange this as described and claimed in my co-pending 30'? application, Serial No. 229,623 filed Sept. 12, 1938, the safety device being mounted directly on the tubular body 5 at a position diametrically opposite to the plug 1 and midway between the fins I4.

The automatic operation of the safety device may influence a push-rod which forces the movable part of the coupling off the terminal pins l2 and so breaks the circuit through the heater.

When the safety device is arranged in metallic contact with the body 5 and midway between the 46? fins I 4 as above described, the fins ensure that when the liquid level has sunk below the part of the body 5 which carries the safety device, substantially all the remaining portion of the heater will still be in contact with the liquid; thus, as the liquid level falls, the portion of the heater adjacent the safety device will be the first to become excessively hot, so that the device will operate in sufiicient time to prevent damage to the resistance winding.

In addition to the provision of downwardly projecting fins on the body 5, those parts of the element other than where the safety device is mounted, may be bodily bent downwards in relawhich maintain I 'tion to the remainder of the heater, or the looped body may be tilted as described in my co-pending application aforesaid.

What I claim then is:

1. In combination, a vessel for holding liquid, an electric heater mounted within said vessel and adapted for immersion in said liquid, said heater comprising a tubular metal body of loop form, said loop being disposed in a plane transverse to said Vessel and spaced above the base thereof, and at least one fin extending downwardly from said body and adapted to maintain contact with liquid in said vessel after the level of said liquid has descended below said body, the free edge of said fin being spaced above the base of said vessel.

2. In combination, a vessel for holding liquid, an electric heater adapted for immersion in said liquid, said heater comprising a tubular metal body of loop form, said loop being disposed in a plane transverse to said vessel and spaced above the base thereof, a plug adapted to be secured in an opening in the wall of said vessel and having the ends of said looped body mounted therein, and at least one fin extending downwardly from said body and adapted to maintain contact with liquid in said vessel after the level of said liquid has descended below said body, the free edge of said fin being spaced above the base of said vessel.

3. In combination, a vessel for holding liquid, an electric heater mounted within said vessel and adapted for immersion in said liquid, said heater comprising a tubular metal body of loop form,

said loop being disposed in a plane transverse to said vessel and spaced above the base thereof, said body having a fiat cross section whose major dimension is substantially perpendicular to the plane of said loop, and at least one fin extending downwardly from the lower edge of said body and adapted to maintain contact with liquid in said vessel after the level of said liquid has descended below said body, the free edge of said fin being spaced above the base of said vessel.

4. In combination, a vessel for holding liquid, an electric heater mounted within said vessel and adapted for immersion in said liquid, said heater comprising a tubular metal body of loop form, said loop being disposed in a plane transverse to said vessel and spaced above the base thereof, and downwardly extending fins provided at oppositely disposed positions on said body and adapted to maintain contact with liquid in said vessel after the level of said liquid has descended below said body, the free edges of said fins being spaced above the base of said vessel.

5. In combination, a vessel for holding liquid, an electric heater mounted within said vessel and adapted for immersion in said liquid, said heater comprising a tubular metal body of loop form which extends transversely of said vessel in spaced relationship to the base thereof, a safety device mounted on said body and operative at a predetermined temperature to cut off the current through the heater, and a fin extending downwardly from said body and adapted to maintain contact with liquid in said vessel after the level of. said liquid has descended below said body, the free edge of said fin being spaced above the base of said vessel, said safety device being disposed on a portion of said body which is spaced from the finned portion thereof, so that it will reach a temperature sufficient to cause its operation before said liquid level has sunk below said fin.

6. In combination, a vessel for holding liquid, an electric heater mounted within said vessel and adapted for immersion in said liquid, said heater comprising a tubular metal body of loop form, said loop being disposed in a plane transverse to said vessel and spaced above the base thereof, a safety device mounted on said body and operative at a predetermined temperature to out off the current through the heater, and downwardly extending fins provided at oppositely disposed positions on said body and adapted to maintain contact with liquid in said vessel after the level of said liquid has descended below said body, the free edge of said fin being spaced above the base of. said vessel, said safety device being disposed on an unfinned portion of said body, so that it will reach a temperature sufiicient to cause its operation before said liquid level has sunk below said fins.

'7. In combination, a vessel for holding liquid, an electric heater mounted within said vessel and adapted for immersion in said liquid, said heater comprising a tubular metal body of loop form, said loop being disposed in a plane transverse to said vessel and spaced above the base thereof, and at least one fin extending downwardly from said body and decreasing in width towards the free edge thereof, said fin being spaced from the base of said vessel and adapted to maintain con tact with liquid in the latter after the level of said liquid has descended below said body.

8. In combination, a vessel for holding liquid, an electric heater mounted within said vessel and adapted for immersion in said liquid, said heater comprising a tubular metal body of loop form, said loop being disposed in a plane transverse to said vessel and spaced above the base thereof, a safety device mounted on said body and operative at a predetermined temperature to cut off the current through said heater, a fin extending downwardly from said body and adapted to maintain contact with liquid in said vessel after the level of said liquid has descended below said body, said fin terminating clear of the base of said vessel and tapering in width in a downward direction, whereby the amount of heat transmitted therethrough to said liquid progressively decreases as the liquid level sinks, the heater reaching the predetermined temperature aforesaid before said fin has been wholly uncovered by said liquid.

WALTER H. BULPITT. 

